Class override in ApiResponseObject

[fabiomaffioletti]

Give the possibility to specify the response object as part of the @ApiResponseObject annotation. For example:

@ApiResponseObject(City.class)

letting it possible to annotate old school servlets:

@ApiMethod(path = "/implicitResponseObject", verb = ApiVerb.GET, description = "a-test-method")
@ApiResponseObject(City.class)
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
...
}

Use the JSONDocTypeBuilder class to build the return type. Please create JSONDocNullType and use it as default class in the annotation declaration.